4 ms·

Citation? I tried googling and couldn't find anything to confirm that. When I searched on half-life, the results that came up mostly seemed to discuss the half

by jcrben 4y ago

Citation? I tried googling and couldn't find anything to confirm that. When I searched on half-life, the results that came up mostly seemed to discuss the half-life in the body, not the half-life in an environmental sink such as the ocean.

mlyle 4y ago
> the results that came up mostly seemed to discuss the half-life in the body Yah, there's a lot of data on "serum" or "elimination" half lives. What you care about is "atmospheric", "aqueous abiotic", and "aqueous biotic" half lives. So, e.g. for PFOA, atmospheric half lives are about 130 days... https://pubs.acs.org/doi/pdf/10.1021/jp036343b https://pubs.acs.org/doi/pdf/10.1021/jp036343b I can't come up with a link to share for PFOA in aqueous solutions, but it looks like 90-150 years.
- jcrben 4y ago
  It's an interesting article from 2004; might not be reading it right but seems like this one from 2020 is less optimistic about hydroxyl radicals (OH) breaking down PFOA in the atmosphere. https://pubmed.ncbi.nlm.nih.gov/31978654/ https://pubmed.ncbi.nlm.nih.gov/31978654/ Your same link notes that the majority of PFOA is not broken down in the atmosphere and points to "wet and dry deposition" mostly, which sounds like it's being dropped down to Earth remaining as PFOA.
  - mlyle 4y ago
    > It's an interesting article from 2004; might not be reading it right but seems like this one from 2020 is less optimistic about hydroxyl radicals (OH) breaking down PFOA in the atmosphere. https://pubmed.ncbi.nlm.nih.gov/31978654/ https://pubmed.ncbi.nlm.nih.gov/31978654/ That's an interesting paper. If so, multiply the atmospheric time by 2-4. > Your same link notes that the majority of PFOA is not broken down in the atmosphere and points to "wet and dry deposition" mostly, which sounds like it's being dropped down to Earth remaining as PFOA. Yes. That doesn't affect the "half life" here. In the end, not much PFOA ends up in the atmosphere in the first place, and most precipitates out to less convenient places where it lives longer. Of the stuff resident in the atmosphere, it does break down on human timescales, at least...

by jcrben 4y ago

mlyle 4y ago

> the results that came up mostly seemed to discuss the half-life in the body Yah, there's a lot of data on "serum" or "elimination" half lives. What you care about is "atmospheric", "aqueous abiotic", and "aqueous biotic" half lives. So, e.g. for PFOA, atmospheric half lives are about 130 days... https://pubs.acs.org/doi/pdf/10.1021/jp036343b https://pubs.acs.org/doi/pdf/10.1021/jp036343b I can't come up with a link to share for PFOA in aqueous solutions, but it looks like 90-150 years.

jcrben 4y ago
It's an interesting article from 2004; might not be reading it right but seems like this one from 2020 is less optimistic about hydroxyl radicals (OH) breaking down PFOA in the atmosphere. https://pubmed.ncbi.nlm.nih.gov/31978654/ https://pubmed.ncbi.nlm.nih.gov/31978654/ Your same link notes that the majority of PFOA is not broken down in the atmosphere and points to "wet and dry deposition" mostly, which sounds like it's being dropped down to Earth remaining as PFOA.
- mlyle 4y ago
  > It's an interesting article from 2004; might not be reading it right but seems like this one from 2020 is less optimistic about hydroxyl radicals (OH) breaking down PFOA in the atmosphere. https://pubmed.ncbi.nlm.nih.gov/31978654/ https://pubmed.ncbi.nlm.nih.gov/31978654/ That's an interesting paper. If so, multiply the atmospheric time by 2-4. > Your same link notes that the majority of PFOA is not broken down in the atmosphere and points to "wet and dry deposition" mostly, which sounds like it's being dropped down to Earth remaining as PFOA. Yes. That doesn't affect the "half life" here. In the end, not much PFOA ends up in the atmosphere in the first place, and most precipitates out to less convenient places where it lives longer. Of the stuff resident in the atmosphere, it does break down on human timescales, at least...